svn commit: r286223 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Peter Wemm]

On Monday, August 03, 2015 11:31:58 AM Steven Hartland wrote:
> On 03/08/2015 10:47, Slawa Olhovchenkov wrote:
> > On Mon, Aug 03, 2015 at 09:34:10AM +0000, Steven Hartland wrote:
> >> Author: smh
> >> Date: Mon Aug  3 09:34:09 2015
> >> New Revision: 286223
> >> URL: https://svnweb.freebsd.org/changeset/base/286223
> >> 
> >> Log:
> >>    Fix KSTACK_PAGES check in ZFS module
> >>    
> >>    The check introduced by r285946 failed to add the dependency on
> >>    opt_kstack_pages.h which meant the default value for the platform
> >>    instead
> >>    of the customised options KSTACK_PAGES=X was being tested.
> >>    
> >>    Also wrap in #ifdef __FreeBSD__ for portability.
> > 
> > /usr/src/sys/kern/kern_proc.c:int kstack_pages = KSTACK_PAGES;
> > 
> > May be check variable kstack_pages is best way?
> > Eliminate dependency on foreign opt_XXXX.
> 
> I did think of that but as other modules such as dtrace, which is also
> cddl code, already have this dependency I went with this.
> 
> I'm easy though, if there's a concusses that kstack_pages or possibly
> curthread->td_kstack_pages, which would take into account the
> possibility of varied thread stack sizes, then I can make that change.
> 
> What do others think?

The whole thing has missing the point.

Changing the default for the entire kernel just because the zfs compat 
wrappers can't be bothered requesting a suitable value is.. unfortunate.. 
particularly when it is in freebsd-provided code, not upstream zfs code.

Fix the kproc_kthread_add() calls in do_thread_create() and zvol_geom_run() 
instead.  Enforce a lower bound there for zfs threads instead of making the 
entire rest of the kernel use more memory.

eg: I'm thinking along these lines:
Index: cddl/compat/opensolaris/sys/proc.h
====================================================
--- cddl/compat/opensolaris/sys/proc.h	(revision 286224)
+++ cddl/compat/opensolaris/sys/proc.h	(working copy)
@@ -77,6 +77,8 @@
 	ASSERT(state == TS_RUN);
 	ASSERT(pp == &p0);
 
+	if (stksize < 16384)
+		stksize = 16384;	/* Enforce lower bound on ZFS threads */
 	error = kproc_kthread_add(proc, arg, &zfsproc, &td, RFSTOPPED,
 	    stksize / PAGE_SIZE, "zfskern", "solthread %p", proc);
 	if (error == 0) {


Beware, some platforms have large pages (eg: ia64 in -stable has 8k, 16k or 
32k pages, from memory).  Specifying an arbitrary number of pages in code 
that's supposed to be portable isn't a good idea.

-- 
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com; KI6FJV
UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246
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